The present invention relates to a grass trimmer.
In the grass trimmer for use in, for example, grass cutting, there is a demand to reduce as much as possible the weight of the head portion including the grass cutting blade, in order to improve the handling characteristics of the machine. Generally, the grass trimmer has an elongated operation rod accomodating a transmission shaft and a gear mechanism through which the transmission shaft is drivingly connected to a blade driving shaft. The gear mechanism is housed by a gear box which is connected to the end of the elongated rod and made by die-casting from a light-weight material such as an aluminum alloy, in order to cope with the above-mentioned demand.
The die-cast articles, however, generally exhibit small resistance to impact. Therefore, when the operation rod is swung to the left and right during the operation of the machine, it is often experienced that the gear box is broken by an impact due to collision with, for example, a large stone. In the worst case, the broken gear box fly dangerously together with the cutting blade away from the rod.